1. Field of the Invention
The field of the present invention relates generally to metal roof systems. More particularly, the present invention relates to metal roof systems that facilitate air circulation from the eave to the ridge between roof layers to improve the useful life and operation of the roof.
2. Background
Many structures utilize metal roof systems to protect the interior of the structure from exposure to the elements, including sun, rain, snow and the like. Metal roofs are utilized on metal, brick, wood and other structures. Generally, the structure is built with interior columns that support a series of rafters or beams attached at the top of the columns. The roof rafters or beams are typically attached in a sloped manner with a ridge at the top to provide positive downward drainage. Spanning the rafters or beams are a series of light gauge metal Z-shaped or C-shaped structural members commonly referred to as purlins. The purlins generally run perpendicular to the rafters or beams and are configured to be in a spaced apart relationship to each other provide structural support for the overlying metal roof system.
One well known and commonly utilized metal roof system for sloped roofs comprises a decking attached to the purlins and a plurality of metal panels attached to the decking with a thermal barrier disposed between the decking and metal panels. The decking material is attached with screws or bolts directly to the purlins that are attached to the roof rafters or beams. Most often, but not exclusively, the decking consists of a plurality of wooden panels, such as plywood, spaced side-by-side on top of the purlins. In many areas of the United States, the thermal and waterproof barrier is placed over the decking material to resist the flow of water, either from rain or snow, into the structure and to provide some degree of insulating effect for the interior of the structure. One common type of thermal barrier comprises roofing (i.e, felt) paper with a plastic covering over the roofing paper. The uppermost part of the roof, the metal panels, are attached to the decking on top of the thermal barrier. A very common type of metal panel utilized for metal roofs is the corrogated steel sheet having a plurality of spaced apart and parallel, alternating ribs and valleys. Although the rib configuration (i.e., the shape and size) varies considerably among the many manufacturers of corrugated panels, the valleys are generally flat to form a lower plane that is spaced apart from the top of the ribs. Threaded screws are typically used to attach the metal panels to the underlying decking.
The above-described roofing system is generally sufficient to obtain a relatively strong, lightweight and weather resistant roof to protect the interior and building components of a structure. A common and well known problem with all metal roofs results from the high thermal conductivity of the metal material used for roofing. During cold weather or when snow is on the roof, the metal roof components will contract. When there is sunshine, even during cold days, the sun will heat up the upper metal panels and the air trapped between the metal panels and the decking. The heretofore standard configuration for metal roofs results in thermal expansion and contraction (i.e., thermal flexing) of the roof in response to temperature changes during the day and through the seasons. In areas of the United States where colder temperatures and/or snow conditions are common in the winter months, the thermal flexing of the roofing material is even more pronounced (particularly on the side of the roof that faces the sun). One well known result of this thermal flexing is that the threaded metal screws will back partially or completely out from the decking to which they were attached. The heating and cooling of the interior of the structure exsasberates this problem by creating back pressure that helps work the screw out. In addition to the obvious problem of reducing the structural integrity of the roof system, the backing out of the screws creates a conduit for moisture to enter into the space between the metal panels and the decking. Once moisture enters this area, it begins to result in the rotting of the thermal barrier and then the underlying decking, thereby damaging the roof and necessitating expensive repairs and/or retrofitting of the roof. Even without the backing out problem, moisture can build-up in between the metal panels and the decking due to the xe2x80x9csweatingxe2x80x9d of the metal panels from the temperature fluctuations of the air trapped therein.
Although the above problem is well known, there are no known solutions that effectively address and prevent the backing out of the screws and the moisture build-up in between the metal panels and decking. One way to reduce the thermal flexing problem and the sweating action is to lessen the amount of temperature changes that affect the roof system. As set forth in the present invention, this can be done utilizing air circulation and the principles of air convection to reduce the thermal flexing effect and maintain the space between the metal panels and the decking in a dry condition to reduce or prevent damage to the roof. Currently there are no known systems for accomplishing this objective.
Builders of structures having metal roofs have long known of the benefits of installing a vent along the roof ridge to vent out air from the attic or interior of the structure. Early vents were as simple as an open slot running along the entire length of the ridge. Later vents were developed to allow air to escape but prevent moisture and other elements from entering the interior of the structure. The ridge vents allow air to vent from the structure by convection airflow and by suction from wind blowing across the roof. Air vents added to the eave (or soffit) of the structure improved airflow by providing passive ventilation through the introduction of fresh ambient air into the attic or interior. As stale, hot air is withdrawn from the structure by convection and/or wind suction at the ridge vent, fresh ambient air is drawn into the attic or structure at the eave vent.
Other inventors have developed a variety of systems for the convection of air from structures having metal roofs. For instance, U.S. Pat. No. 5,765,329 to Huang describes roof venting system for metal roofs using two sets of corrugated metal sheets with spacers between the sheets to vent hot air to the atmosphere through a plurality of apertures in the corrugated sheets for improved heat radiation, heat insulation and the withdrawal of gasses from the interior space of the building. U.S. Pat. No. 5,826,383 to Garrison describes a roof venting system that utilizes ridge venting and eave venting to vent hot air from the interior of the building while preventing water, debris and pests from entering the interior of the building. U.S. Pat. No. 5,561,953 to Rotter describes a roof ridge ventilation system for metal roofs to allow vapors inside the building to vent out through an air permeable, resilient member located at the roof ridge. U.S. Pat. No. 5,367,848 to McConnohie describes a bracket for use to attach a new metal roof over the ribbed panels of an existing corrugated metal roof.
The above-described patents demonstrate that it is well known to ventilate structures having sloped roofs by utilizing vents at the top ridge of the roof and/or at the eave of the roof. These patents generally describe various roof systems for ventilating the interior of the structure through the roof itself or through ridge or eave vents attached thereto. However, none of the related art describe, singularly or in combination, a simple, easy to install system to improve air circulation between the metal roof panels and the decking to reduce the amount of thermal flexing in order to prevent the well known problem of the metal screws backing out. Consequently, a need exists for a metal roof system that is inexpensive to manufacture and easy to install, yet which induces air circulation between the metal roof panels and the decking to prevent the backing out of screws due to thermal flexing.
The metal roof system of the present invention provides the benefits and solves the problems identified above. That is to say, the present invention provides a metal roof system that is inexpensive to manufacture and easy to install to reduce or eliminate the likelihood of the screws backing out of the metal roof panels and creating conduits for the entry of moisture into the roof system. In addition to the above benefits, the present invention increases the circulation of air to improve insulation and reduce moisture migration.
The present invention is directed to a structure having a sloped metal roof with a first end and a second end thereon, such that the roof slopes in a generally downward direction from the roof ridge at the first end to the eave at the second end. The metal roof system of the present invention comprises a lower decking layer, an upper metal panel layer and a spacer disposed between the decking and metal panels. In certain parts of the United States it is advantageous to include a thermal barrier layer between the decking and the spacers to further protect the decking. The decking is generally attached to the roof rafters, or to purlins attached to the roof rafters, with the use of screws and the like, as are suitable for securely fastening the decking to the structure. Typically, the decking is made from a plurality of plywood panels laid side-by-side across the entire roof of the structure. The metal panels can comprise a plurality of corrugated metal sheets joined together side-by-side across the roof and attached to the spacers on the decking utilizing metal screws or other fastening devices for securely fastening the metal panels to the spacer. The typical metal panel has a series of spaced apart, alternating ribs and valleys, with the valleys being generally flat to form a planar bottom. The metal panels are joined to the spacers at the flat valleys.
In the preferred embodiment of the present invention, the spacer comprises a shaped member configured to have a generally planar top section to abut the planar surface formed by the flat valleys of the metal panels, a generally flat bottom section to abut the planar surface of the decking and a center section that vertically disposes the top and bottom sections in a spaced apart relationship. The bottom section of the spacer attaches to the decking or the rafters or purlins under the decking using the appropriate wood or metal screws. The metal panels attach to the top section of the spacer at the flat valley portions of the metal panels using metal screws or the like. The center section includes one or more openings therein to form an airflow cavity between the decking and the metal panels. In the preferred embodiment, the center section has a plurality of openings sized and configured so as to not substantially reduce the strength and carrying capability of the spacer.
The preferred embodiment of the metal roof system of the present invention also includes a ridge vent at the first end of the metal roof. The ridge vent should be configured to be in fluid flow communication with the airflow cavity created by the spacers between the metal panels and the decking so as to allow hot, stale air to be withdrawn through the ridge vent by convection airflow and/or wind suction across the roof ridge. Preferably, the metal roof system also includes an eave vent disposed at the second end of the metal roof. The eave vent should also be in fluid flow communication with the airflow cavity so as to facilitate passive ventilation through the introduction of fresh ambient air into the airflow cavity and out the ridge vent. In this manner, the effects of changing temperature will have less impact on the metal roof system and will reduce or eliminate the thermal flexing that results in the backing out of the screws that fasten the metal panels to the spacer. Because the screws or other fasteners will remain in place, conduits for the transfer of moisture from the exterior to the interior of the roof will not form and result in rotting of the thermal barrier or decking underneath the metal panels. In addition, the circulation of air between the metal panels and the decking will eliminate or reduce the sweating effect that can also result in moisture build-up.
Accordingly, the primary objective of the present invention is to provide a metal roof system which can be inexpensively made and easily installed on metal roofs to improve the useful life of the roof and reduce roof repair and/or replacement costs.
It is also an important objective of the present invention to provide a metal roof system that utilizes a spacer, having one or more openings therein, disposed between the metal panels and the underlying decking to form an airflow cavity for the circulation of air between the decking and metal panels.
It is also an important objective of the present invention to provide a metal roof system that connects an airflow cavity created between the metal panels and underlying decking to air vents located at the roof ridge and eaves to allow ambient air to be drawn in at the eave vent and circulated through the airflow cavity and out the ridge vent to the atmosphere in order to reduce or eliminate thermal flexing that can result in the creation of conduits from the backing out of screws.
It is also an important objective of the present invention to provide a metal roof system that utilizes a spacer having generally flat top section, a generally flat bottom section and a center section, having one or more openings disposed therein, that interconnects the top and bottom sections in a spaced apart relation.